(gdb) where
#0  0xb6d954ec in syscall () from /lib/libc.so.6
#1  0xb5fa27d4 in QMutexPrivate::wait(int) () from /usr/lib/libQtCore.so.4
#2  0xb5f9eb9c in QMutex::lockInternal() () from /usr/lib/libQtCore.so.4
#3  0xb6ac5b48 in data_in(char*, int) () from /usr/lib/libvt.so
#4  0xb6a8dbec in codesys_send () from /usr/lib/libvt.so
#5  0xb6b567a0 in IsoVtLib_NumericValue () from /usr/lib/libIsobus.so
#6  0xb6b55574 in isocmd_numericvalue () from /usr/lib/libIsobus.so
#7  0xb52799a0 in ?? ()
#8  0xb52799a0 in ?? ()